Mac sales bottomed out in February, says analyst

February is going to turn out to have been a dismal month for Mac sales — especially compared with last year — says Piper Jaffray analyst Gene Munster. But they should bounce back a bit in March, he adds.

The data on which Munster bases his predictions — domestic sales estimates made by the NPD Group — won’t be released until next Monday, March 16. But that didn’t stop Munster from posting the numbers shown in the chart above. (The last two data points are his estimates.)

“We expect Mac NPD to bottom out at around -12% y/y [year over year] in the month of Feb-09,” he writes in a report to clients issued Tuesday. He cites two key factors:

A tough comparison with February 2008, when unit sales got a bump from the new Macbook Air, which went on sale that month.

A slowdown in Mac sales from customers anticipating the release of new machines — the iMacs, Mac minis, and Mac Pros introduced March 3.

March should look a little better for Apple thanks to sales of those new machines, says Munster. He expects NPD data to be flat for the month, which would leave Mac sales for Apple’s second fiscal quarter down 6% — the first quarter of negative Mac sales growth since at least 2005.

The chart above shows both how strong Mac sales were at the start of 2008 and how much they have slowed with the onset of the recession.

The good news, according to Munster, is that the worst may be over. He expects “positive sentiment” to build after the February trough and push share prices up over the next several weeks.

Piper Jaffray’s target for Apple AAPL is $180 per share. The stock closed Tuesday at $88.63 — up 6.64% for the day.